Grinding wheel is the most important type of abrasive tool in grinding process. The grinding wheel is made by adding bonding agent during the grinding process, processing the embryo, drying and burning the embryo.

As a kind of grinding tool, the grinding wheel is very different from the saw blade in people’s impression. Its appearance is not sharp. The surface of the grinding wheel is rough and uneven, showing a granular shape with different specifications. Objects, this is helpful to increase the friction and contact force of the grinding wheel, so that the objects to be ground can be ground more smoothly.

Resin grinding wheel is a grinding wheel made of resin with high strength. It is widely used in cutting discs, double end faces, heavy-duty grinding wheels, polishing wheels and so on. It has the characteristics of certain elasticity, low heat resistance, good self-sharpening, easy production, and short process cycle; it is widely used for rough grinding, barren grinding, cutting and free grinding, such as grinding steel ingots and casting burrs.

Changzhou Dome Abrasives Manufacture Co., Ltd founded in 1997,it is a leader abrasive disc manufacturer in China with more than 120 employees, the daily production capacity reaches 300,000 pieces.

The factory located at Changzhou City, Jiangsu provice,China, which is 150 kilometers from Shanghai. It is very convenient to ship the goods from Shanghai or Ningbo sea ports, also convenient send the goods to Yiwu warehouse.

At present, our factory can produce 3” to 16” different size cutting disc, the thickness from 1.0mm to 3mm with T41 flat and depressed center T42 types. 4” to 9” grinding wheels wiht thickness 6.0mm to 7.0mm with double nets or three nets for your choice. Most of our products already past CE and Germany MPA certificates.

The products widely export to North and South American countries, Europe countries, East and South East Asia countries, Africa and Middle East countries.

Some manufacturers are troubled by many quality problems in the resin grinding wheel production process. Today, the editor specially found some common problem analysis and solutions. I hope to communicate and learn with you~

1 Material granularity and hardness are not consistent.

Calculate the ingredients strictly according to the ingredient list, and review is the key procedure.

2 Inclusion

Before and during the mixing process, clean up the tooling and equipment. Before ingredients, check the various raw materials for impurities.

3 Uneven mixing

Mix according to the mixing time required by the process. Replace parts of the mixer that are too worn at any time. The powdered resin material should be sieved according to the screen number and frequency specified in the process.

4 Uneven organization, uneven hardness and unbalance

Adjust the dry humidity of the mixture to make it have good moldability. Spread and scrape materials according to process requirements. According to the process requirements, first use the shim to maintain the accuracy of the press; when feeding, the material is unevenly spread, the mixture is wet, or the material is agglomerated, the feeding is uneven, the mold is worn, and the material leakage is serious. The mold needs to be replaced.

5 Cracks in the molded body

The hot pressing temperature is too high, the product is very cold and hot, and the temperature is too low when the core type is removed. The core type should be removed in time. The raw material is damp and deteriorates, or the compound is wrong.

The following four crack prevention measures:

The plasticity of the mixture is good for speed control;The molding tool must not exceed the specified wear standard;The template and the shim should maintain good flatness;The thickness of the shim must be consistent, and the elasticity of the spring shim must be consistent. Unload the mold in the order specified by the process.

6 End face crack

The molding material has poor plasticity, and the unloading method is improper. The bottom plate of the forming mold is not flat or the backing plate is not too parallel.

7 Peripheral cracks

The mold sleeve is seriously worn, and the mold sleeve is too skewed when unloading the mold sleeve.

 8 Aperture crack

The strength of the blank is low, the vibration is too large when unloading the mold, the core rod is too worn or the taper is too small, and the unloading sequence does not meet the process regulations.

9 Diagonal crack

The selected spring pad iron has inconsistent elastic force, which makes the mold deflection and compression produce diagonal lines. The pressing speed of the fine material abrasive tool is too fast, the pressure maintaining time is short, and the mold fit gap is too large.

10 Both ends are not parallel

Maintain the accuracy of the press table and operate according to the process regulations.

11 Uneven surface

Tooling equipment is maintained within the required accuracy range.

12 Molding hardness does not match

The first piece of pressing must be inspected, and each batch of blanks shall not be less than 30%. Check the weighing unit often and observe whether the pressure changes.

13 The bridge is uneven

The cooling needs to be uniform; the surface of the part that is “warped” without a flat surface is called a bridge. This is caused by uneven shrinkage of the workpiece or uneven backing plate of the furnace due to uneven cooling. Mostly come from thin-slice grinding wheels and fine-grained thin products. When the cooling speed of the flake grinding wheel is too fast, it is easy to produce bridge waste.

14 Bubble

According to the hardening curve of the product specification, the temperature is controlled and the compounding process is strictly controlled. The molding temperature is too high or too low, and the temperature needs to be adjusted. The curing temperature is too high and the curing oven temperature is out of control. The bonding agent is mismatched; the surface of the super-hard abrasive is deformed locally or the entire surface swells, and shows a resin luster, and some have turtle-shaped cracks.

Causes:
1.Too fast heating speed or large temperature fluctuations can easily cause foaming and swelling of parts with fine particle size, high hardness and tight organization. Because this kind of product contains a large amount of binding agent or small pores, if the temperature is not accurately controlled and the heating speed is too fast, it will cause the binding agent to react fiercely, the amount of volatile matter will increase sharply, and the high gas pressure inside the blank will cause the product to foam and expand.
2.The type material is not uniformly mixed, there is a binding agent in the material, or contains more solvents with lower boiling points (such as ethanol, acetone).
3.Due to errors in the mixing and molding process, the combined dosage of the parts increases, the unit weight increases, and the pressure increases.

15 Deformation and collapse

The furnace is installed and the temperature is controlled according to the process regulations. The ratio of fillers should be strictly controlled and adjusted, and there is an interaction between fillers. Insufficient pressure will cause deformation when cutting sheets are stacked.

The causes of deformation and collapse of super-hard abrasive tools during the hardening process are:
1. When the furnace is installed, the green body is exposed outside the hardened backing plate or the green bodies are squeezed against each other, and the backing plate is not flat so that the green body is inclined.
2. High-thickness parts are not filled with paper and sand according to the process regulations.
3. Natural drying time is short or directly into the furnace to harden without low-temperature drying.
4. The heating speed is too fast, and the binder melts sharply to make the body soften and then collapse.

16 Hearts

The exhaust system of the hardening furnace needs to be unblocked, and the hardening operation according to the hardening curve of the product specification should be correctly controlled. The blank of the liquid resin material should be selected from the porous backing plate or the ceramic backing plate; redness occurs in the center of the super-hard abrasive, which causes the hardness of the grinding wheel All are easy to break.
Cause:
1. The exhaust system of the hardening equipment is poor and the exhaust gas is difficult to discharge.
2. The hardening curve is unreasonable, and the heating rate is too slow.
3. The backing plate of the liquid resin blank has poor air permeability.
4. The resin free phenol content of the liquid resin material is too high and the solid content is too low.

17 Inconsistent hardening hardness and rotating fracture

According to the correct temperature control operation of the hardening curve, the powdery resin blanks must be covered or buried in the hardening. During the loading, unloading and handling process, the blanks are prevented from being shocked. The super-hard abrasive tool breaks during inspection rotation, which is caused by low bonding strength or cracks in the grinding.
The reason is:
1. The hardening temperature is too high, and the bonding agent has been partially carbonized to reduce the strength of the abrasive.
2. Compounding errors, such as more abrasives and less binders, or poor quality of the binder itself reduces its strength.
3. Severe vibration during mold unloading, transportation and furnace loading caused mechanical damage to the parts and dark cracks inside.
4. The structure of the grinding wheel is uneven, and the unbalanced grams is too large.
5. The grinding wheel is seriously eccentric or the hole diameter is too large.

18 The cutting disc is off the net during use

The quality of the resin powder and the resin liquid and the mesh should be qualified, and the process formula should be reasonable, basically there is no such problem. In some fractures, the abrasive grains are coarse, the structure is loose, and the bonding agent is missing, and the mesh will be separated by a little pull. These defects are related to improper manufacturing process.

19 The hardness and strength of the finished product do not match
1. The quality of the resin is unstable, and the free phenol content of the resin fluctuates. The so-called free phenol is the phenol remaining in the resin. The molecular formula is C6H5OH. Long-term heating can crack the hardened resin and affect the strength of the grinding wheel.
2. Resin powder and urotropine are not uniformly mixed. The scientific name of urotropine is hexamethylenetetramine ((CH2)6N4). As the hardener of the resin, the amount of urotropine is insufficient and the resin hardening is not complete. , Affect the strength and hardness of the grinding wheel; if the content is too high, the excess urotropine will not be combined with the resin, and will decompose and volatilize during the hardening process, which will increase the pores of the grinding wheel and reduce its strength and hardness.
3. The particle size of the bonding agent is too coarse, and the particle size of the bonding agent is preferably fine, which is conducive to uniform distribution of the bonding agent and full contact of the hardener. If the particle size is too coarse, the molding material is not easy to mix uniformly, which affects the hardness and strength of the grinding wheel. Even for resin flake cutting wheels and cymbal-shaped wheels with coarser particle size, the selected binder (resin powder) particle size should be finer than 320#. To manufacture fine-grained grinding wheel products, the particle size of the bonding agent is required to be several microns.

20 Edge drop and corner drop

After forming and hardening, it should be operated carefully to ensure that the edges of the part are intact and avoid mechanical damage. Falling edges and corners are mostly caused by careless handling during furnace installation and transportation. Workers who are unskilled in operation should be trained to improve their skills. The resin mold body has a low wet strength and should be transferred or taken and placed by the flip method, and the body cannot be directly moved by hand.